Anyone out there with experience in winter camping? I mean really cold weather winter camping, 0 to -20 degrees. My son's Boy Scout Troop is planning their next high adventure trip. We are going to Northern Tier Okpik. I've done some winter camping in 20 to 0 degrees and survived but I'm looking for as much information as I can find. Anyone have suggestions for websites to find more info on gear and how to stay comfortable?